Probing Colliding Wind Binaries with High-Resolution X-ray Spectra

X-ray line profiles represent a new way of studying the winds of massive stars. In particular, they enable us to probe in detail the wind-wind collision in colliding wind binaries, providing new insights into the structure and dynamics of the X-ray-emitting regions. We present the key results of new analysis of high-resolution Chandra X-ray spectra of two important colliding wind systems, γ² Velorum and WR140. The lines of γ2 Vel are essentially unshifted from their rest wavelengths, which we suggest is evidence of a wide shock opening angle, indicative of sudden radiative braking. The widths of the lines of WR140 are correlated with ionization potential, implying non-equilibrium ionization. The implications of these results for the radio emission from these systems are discussed, as are some of the future directions for X-ray line profile modeling of colliding wind binaries.